JPH0964651A - Electronic circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To remove a defect that the efficiency of a high output amplifier is reduced when the voltage of a battery is high. SOLUTION: A constant voltage circuit is connected between the drain of the high-frequency amplifier and the battery to apply fixed voltage of >=70% to <=85% of the voltage of the charged battery to the drain of the amplifier. Thus voltage to be impressed to the drain of the high-frequency amplifier can be fixed and the reduction of efficiency can be prevented.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high output amplifier for transmission, an antenna, and a battery-driven electronic circuit including the same, and more particularly to an electronic circuit suitable for improving the stability of characteristics.

[0002]

2. Description of the Related Art FIG. 2 shows a microwave transmitter / receiver used for mobile communication. This device is described in Hashimoto, “Outline of microwave device”, Mitsubishi Electric Technical Report, vol.64, No.9, pp706-711, 1990. This device is composed of a receiver for receiving radio waves from a satellite and a transmitter for emitting radio waves toward the satellite. After the radio wave received by the antenna is amplified by the low noise amplifier, the phase shift is adjusted by the phase shifter according to the reception direction of the radio wave. Next, after being mixed with the signal from the local oscillator in the mixer section and converted to an intermediate frequency that is easy to handle,
Demodulated. On the other hand, on the transmitting side, the modulated intermediate frequency wave is radiated from the antenna toward the satellite after being converted to a high frequency and amplified by the mixer section.

FIG. 3 shows a simple block diagram of a high power amplifier. The high power amplifier is composed of a high power field effect transistor (FET) and an impedance matching circuit provided on the input side and the output side. High-power amplifiers are required to produce output power determined by a certain standard. Higher output and higher efficiency amplifier can be realized as the voltage applied to the drain is higher. Therefore, in a battery-powered microwave transceiver such as a mobile phone, a high output FET
The voltage applied to the drain of is the power supply voltage (battery voltage, that is, the maximum voltage).

For example, as shown in FIG. 4, there is a problem that the voltage of the battery decreases with discharge, and therefore, the design has been made so that the performance is maximized at the lowest voltage when the battery is discharged. Here, the minimum voltage of the battery at the time of discharging is, for example, the minimum voltage of the battery when the battery is used up to near its full capacity (1050 mAh) is 2.8 V (this voltage is 70% of the voltage at the time of charging).
Equivalent to 70% of the total capacity of the battery (735 mA)
The minimum voltage of the battery when used up to h) is 3.4 V (this voltage corresponds to 85% of the voltage during charging). However, when such a design is performed, there is a problem that the efficiency decreases when the voltage of the battery is high.
As a specific example, FIG. 5 shows data when the minimum voltage of the battery is considered to be 3V and the design is performed so that the drain voltage = 3V gives the best performance.

[0005]

In the prior art, for example, as shown in FIG. 5, there is a problem that the efficiency decreases when the battery voltage is high.

It is an object of the present invention to provide an electronic circuit capable of keeping the drain voltage of a high power amplifier constant in order to prevent this efficiency drop.

[0007]

A battery-driven electronic circuit according to the present invention includes a high-power amplifier for transmission, an antenna, and a constant voltage circuit, and the constant voltage circuit has a voltage of 70 when charging the battery. %, And a constant voltage of 85% or less is applied to the drain of the high-power amplifier.

[0008]

According to the present invention, since a constant voltage can be applied to the drain of the high-power amplifier, the efficiency can be prevented from lowering.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 6 is a block diagram of a high output amplifier according to an embodiment of the present invention. The difference from the conventional example shown in FIG. 3 is that a constant voltage circuit is provided between the power supply and the drain of the high output FET. This constant voltage circuit is a device that functions to keep the drain voltage of the high-output FET at a constant voltage lower than the power supply voltage. For example, by setting this voltage to the minimum usable voltage (for example, 3V) of the battery,
It is possible to prevent a decrease in efficiency as shown in FIG. As described in the conventional example, the constant drain voltage of the high-output FET is 7 times the battery voltage during charging.
It is considered preferable that the content is 0 to 85%. Further, here, for the sake of simplicity, the high output FET has a single-stage structure, but it may have a multi-stage structure. In this case, since the characteristics of the high-power amplifier are determined by the final-stage FET, it is sufficient to keep at least the drain voltage of the final-stage FET as described above.

Next, FIG. 1 shows a block diagram of a high power amplifier of one embodiment of the present invention including a detailed structure of a constant voltage circuit. In addition,
The constant voltage circuit in this figure is described in Shimizu, "Design of stabilized power supply circuit", CQ publisher, pp24-25. The stabilization principle of this constant voltage circuit will be described below. First, the unstable battery voltage Ei is sent to the load RL through the control transistor Tr1. Next, the resistor R1
And R2 divide the output voltage, and this voltage is compared with the reference voltage provided by the constant voltage diode DZ. Then, the variation of the output voltage is amplified by the error amplifier including the transistor Tr2 and its load resistance R,
It is sent to the input of the control transistor, that is, the base.

If the output voltage is lowered due to the fluctuation of the power supply side or the load side, the change of the output power is caused by a transistor which is an error amplifier through a voltage dividing circuit.
Since the voltage is sent to the base of Tr2 and the reference voltage is constant, the base-emitter voltage of Tr2 decreases and its collector current decreases. As a result, the collector voltage of Tr2, that is, the base voltage of the control transistor Tr1 rises, and therefore the emitter potential of Tr2 also rises.
The previous drop in output voltage will be canceled. From the above, the output voltage is always maintained at a constant value even if the battery voltage and load change. The output voltage Eo of the constant voltage circuit is given by the equation 1.

[0012]

[Equation 1] Eo = (R1 + R2) / R2 * (Vz + Vbe)
(R1 + R2) / R2 * Vz Vz: Reference voltage Vbe: Base-emitter voltage of the error amplifier Tr2 The constant voltage circuit shown in FIG. 1 is an example, and another configuration having the same function may be used. I don't mind.

The low-noise amplifier comprises a low-noise FET and an impedance matching circuit provided on the input side and the output side, like the high-output amplifier shown in FIG. Low noise F
The ET employs a gate length shorter than that of the high output FET in order to improve the characteristics. Therefore, a drain voltage lower than that of the high output FET is sufficient. Therefore, FE for high output
The voltage applied to T and the drain of the low noise FET may be the same constant voltage.

[0014]

According to the present invention, since the voltage applied to the drain of the high-power amplifier can be kept constant, it is possible to prevent the efficiency from lowering.

[Brief description of drawings]

FIG. 1 is a circuit diagram of a high power amplifier according to an embodiment of the present invention including a detailed structure of a constant voltage circuit.

FIG. 2 is a block diagram of a conventional microwave transmitter / receiver device.

FIG. 3 is a block diagram of a conventional high output amplifier.

FIG. 4 is a characteristic diagram showing discharge characteristics of a lithium battery.

FIG. 5 is a characteristic diagram showing voltage dependence of efficiency of a high output amplifier.

FIG. 6 is a block diagram of a high power amplifier according to an embodiment of the present invention.

Claims (5)

[Claims] 1. A battery-powered electronic circuit, wherein the electronic circuit has a high-power amplifier for transmission, an antenna and a constant voltage circuit, and the constant voltage circuit has a voltage of 70 when charging the battery.
An electronic circuit, wherein a constant voltage of not less than% and not more than 85% is applied to the drain of the high-power amplifier. 2. The electronic circuit according to claim 1, wherein the high-power amplifier has a plurality of field effect transistors (FETs). 3. The electronic circuit according to claim 2, wherein the F
ET is an electronic circuit that is made of a compound semiconductor. 4. The electronic circuit according to claim 1, wherein the electronic circuit has a low noise amplifier for reception, and the voltage applied to the drain of the low noise amplifier is a voltage applied to the drain of the high power amplifier. An electronic circuit characterized in that an equal constant voltage is applied and the antenna is shared for reception. 5. A communication device using the electronic circuit according to any one of claims 1 to 4.